Improvements in or relating to combustion chambers

ABSTRACT

An annular combustion chamber comprising a plurality of ducts adapted to inject axially in an upstream direction a gasiform mixture containing vaporized fuel, each duct being associated with a pair of radial nozzles adapted to inject into said chamber two air jets directed toward one another, the geometrically defined area in which the jets are to meet being located at the outlet end of said duct.

United States Patent Inventors Appl. No. Filed Patented Assignee JacquesEmile Jules Caruel Dammarie-les-Lys;

Herve Alain Quillevere, Issy-les- Moulineaux; Louis Jules Banger,Vanves, France May 5, 1969 May 25, 197 l Societe Nationale D'Etude Et DeConstruction De Moteurs DAviation Paris, France IMPROVEMENTS IN ORRELATING TO COMBUSTION CHAMBERS 1 Claim, 2 Drawing Figs.

U.S.Cl 60/39.71, 431/352 Int.Cl F02g 1 00 FieldoISearch (so/39,71;431/242,352

If ZQQ 100 9c 1/ J [56] References Cited UNITED STATES PATENTS 2,807,3169/1957 Jackson 431/352 2,956,404 10/1960 Kassner et al 60/39.712,977,760 4/1961 Soltau et al. 60/39.71X 3,430,443 3/1969 Richardson etal. 60/39.71X FOREIGN PATENTS 1,035,316 4/1953 France 431/352 PrimaryExaminer--Carroll B. Dority, Jr. AttorneyWatson, Cole, Grindle andWatson ABSTRACT: An annular combustion chamber comprising a plurality ofducts adapted to inject axially in an upstream direction a gasiformmixture containing vaporized fuel, each duct being associated with apair of radial nozzles adapted to inject into said chamber two air jetsdirected toward one another, the geometrically defined area in which thejets are to meet being located at the outlet end of said duct.

HMPROVEMENTS IN OR RELATING TO COMBUSTION CHAMBERS Our invention has forits object an annular combustion chamber intended chiefly for gasturbine engines and has more particularly for its object an improvementfacilitating the initiation and stabilization of the flame in theupstream region of such a combustion chamber.

it is known for stabilizing a flame in the upstream region of acombustion chamber, to produce in said region such large and stablereversed streams, that the average duration of the stay in said upstreamregion of burning particles is increased. A known method for thispurpose consists in resorting to impacts between fluid jets and moreparticularly air jets, a fraction of the throughput of which isrecirculated towards the upstream region of the combustion chamber andproduces in said region an eddying flow facilitating the initiation andmaintenance of the combustion, whereas the remainder of said jets flowsdirectly towards the outlet end of the combustion chamber. Such a methodimplies a difficulty inasmuch as the impact point between oppositelydirected jets is not stable and consequently the intensity of theeddying phenomena observed in the upstream region of the combustionchamber may be subjected to large fluctuations which cannot be foreseenand which may jeopardize the stability of the combustion.

it has already been proposed to stabilize the impact between two jets offluid moving in opposite directions with a view to increasing theeddying phenomena in the upstream region of a combustion chamber byresorting to a baffle located in the geometrically defined area in whichthe jets are to meet. it has been found as a matter or fact that the useof such a baffle preventing the direct impact between the two jets andforming an element subdividing symmetrically the recirculated stream maycooperate in the production of a very marked stabilizing effect for saidstream together with an increase of its flow rate.

Such advantages are obtained however at the expense of a number ofdrawbacks among which may be mentioned in particular, in addition to amore intricate structure of the chamber, the difficulty of protectingagainst heat such a baffle subjected to a very high temperature whileadditional losses of head are incurred.

Said drawbacks are cut out in the case of a combustion chamber arrangedas will be explained hereinafter.

According to our invention, there is provided an annular combustionchamber comprising a plurality of ducts adapted to inject axially in anupstream direction a gasiform mixture containing vaporized fuel, eachduct being associated with a pair of radial nozzles adapted to injectinto said chamber two air jets directed towards one another, thegeometrically defined area in which the jets are to meet being locatedat the outlet end of said duct.

it is thus apparent that is is no longer necessary to resort to one ormore independent baffles. The design of the combustion chamber isconsequently simplified. Any further loss of head is cut out, while thecooling of the walls of the baffle is ensured by the vaporization of thefuel and the movement in an upstream direction of the reversed stream isinitiated by the jet of vaporized fuel. There is thus obtained theunexpected result (namely, the stabilization of the point of impactbetween oppositely directed jets of fluids) for which the vaporizingmeans had never been designed hitherto, and which in fact in all knownformer applications had never been achieved.

The following description referring to the accompanying drawings givenby way of example and by no means in a limiting sense will allow ourinvention to be readily understood. In said drawings:

FIG. 1 is an axial sectional view of an annular combustion chamberadapted to operate with fuel vaporizing means and incorporatingstabilizing means designed in accordance with our invention.

FIG. 2 is a sectional view through line "-11 of FIG. 1.

The combustion chamber provided with fuel vaporizing means, which hasbeen illustrated, includes as well known in the art an outer casing laand an inner casing 1b which are substantially coaxial and definebetween them an annular space inside which two substantially coaxialwalls 20 and 2b define the actual combustion chamber. The latter isclosed at its upstream end by an annular cap or dome 3 inside which isfitted an annular structure 4. Said dome 3 and annular structure 4 areprovided with two series of openings 5 and 6 distributed uniformly roundthe axis XX of the combustion chamber, the cooperating openings in thetwo series being in axial alignment with each other. Fuel vaporizingmeans designated by the general reference number 7 are fitted with aclearance coaxially inside each opening 6. The upstream region of thecombustion chamber is connected through at least one duct 8 with asupply of a combustion-supporting fluid such as compressed air. Said airflows through the annular passages extending between the casing 1a, lband walls 2a, 2b and enters the combustion space through the openings 5to form primary air, and through ports 9a and 9b to form cooling air. italso enters through nozzlelike ports 10a and 10b as diluting air andthrough nozzlelike ports 11a and 1 1b as secondary combustion supportingair. The ports 9a, 9b are advantageously directed substantially parallelto the axis of the combustion chamber whereas the ports 10a, 10b arepreferably directed in a substantially radial direction across the walls2a, 2b.

The ports 11a, 11b extend also in a substantially radial directionacross the walls 2a2b in transverse registry with the preliminaryvaporizing means 7 and cooperate in the stabilization of the flame inthe upstream region of the combustion chamber as disclosed hereinafterwith further detail.

Each of the preliminary vaporizing means 7 includes in a conventionalmanner a tubular duct 12, the upstream end of which is housed coaxiallyinside the openings 5 and 6. Said duct branches at its downstream end soas to form two trans-- verse tubular ducts l3 and 14 which are bent backthrough 90 in an upstream direction as illustrated at 15 and 16. A duct17 feeding liquid fuel opens into the upstream region of each duct 12. i

The cross section of opening 6 has a larger size than the duct 12 and itallows positioning round the latter a member 18 which may be rigid withsaid duct. Said member 18 is provided with two extensions 19 and 20defining with the duct 12 and the structure 4 two passageways 21, 22through which a small fraction of the flow of primary air may enterdirectly the combustion space.

During operation, the larger fraction of the primary flow of air enterstogether with the liquid fuel the fuel vaporizing means, the walls ofwhich are subjected along their outer surfaces to the action of theflame. Consequently the fuel is vaporized in said means and the mixtureof air and vaporized fuel escapes substantially axially from the ducts13, 14 in a direction opposed to the general direction of flow ofthecombustion gases, that is towards the cap or dome 3. The small amountof air injected through the passageway 21 round the duct 12 servesmainly for'ensuring a certain thermal insulation of the upstream portionof the fuel vaporizing means 7.

The ports 11a, 11!; provide for the production of two groups ofsubstantially radial jets, the directions of which face each other. Inknown arrangements, the corresponding jets illustrated by the arrows Faand Pb would impinge against each other and a fraction of the fluidforming said jets is then returned in an upstream direction so as toproduce within a region adjacent the cap or dome 3 an eddying areaadapted to facilitate the initiation and maintenance of the combustion,whereas the other fraction of said fluid flows directly towards thedownstream end of the combustion space.

The impact between said oppositely directed jets is however not stableand, in order to remove said lack of stability which has consequentialeffects on the intensity of the turbulent phenomena occurring in theregion of the chamber adjacent the cap 3, it has already been proposedas mentioned hereinabove to insert along the geometrical locus of impactbetween the jets a baffle preventing any direct impact between jets andforming a symmetrically arranged member within the reversed fluid flow.The introduction of such a baffle constituted for instance by one ormore plates however makes the structure of the chamber more intricateand leads to additional losses of head and furthermore it is necessaryto solve a problem of protection against heat by reason of the very hightemperatures prevailing in the region of the chamber enclosing thebaffle.

According to our invention, the baffle is constituted by the outlet endof the fuel vaporizing means, which outlet end is suitably located withreference to theinjection ports 11a, 11b. As illustrated in the drawingsthe oppositely directed jets Fa, Fb extend in the transverse planedefined by the outlet openings of the rearwardly directed ducts l5 and16, such an arrangement providing the advantage of initiating andmaintaining the reversed flow of fluid. lt also facilitates theproduction of eddies.

Obviously the use as a baffles, of elements forming part of the fuelvaporizing means, that is of elements already present but which had notbeen made use of hitherto, for that purpose is advantageous for manyreasons. It does not lead to any additional loss of head within thechamber and cuts out the problem of the cooling of the baffles, whichproblem is solved by the vaporization of the fuel within the ducts ofthe fuel vaporizing means, and these advantages are obtained at theexpense of a very small modification in the structure of the chamber,consisting in the mutual matching between the location of the ports 11a,11b ensuring the injection of and the fuel vaporizing means.

Our invention provides furthermore the advantage of homogenizing morespeedily the combustion region as the mixture of primary air andvaporized fuel is injected at the point of origin of the eddies.

lclaim:

1. An annular combustion chamber fed with liquid fuel and compressed aircomprising:

two coaxial annular casings enclosing between them an annular space;

two coaxial annular walls coaxial with said casings, housed within saidannular space and the interval between which defines an annularcombustion space through which the combustion gases are adapted to flow,said walls defining between them and the corresponding casings annularpassages;

means adapted to supply said annular passages with compressed air;

a dome closing the combustion space at one end thereof;

a plurality of means adapted to inject into the region of the combustionspace lying in the vicinity of the dome vaporized fuel, each of saidmeans having an outlet opening facing the dome and through whichlast-mentioned vaporized fuel is exhausted towards the dome in adirection substantially parallel to the axis of the annular walls, saidoutlet openings being distributed along an annular line extending atsubstantially equal distances from the said annular walls; and

a plurality of nozzlelike ports extending across said annular walls andconnecting each of the annular passages with the annular combustionspace, a nozzlelike port across one annular wall registeringsubstantially radially with a corresponding nozzlelike port across theother annular wall and with a corresponding outlet opening through whichvaporized fuel is exhausted said dome having openings adjacent saidplurality of means for injecting vaporized fuel, deflector meanssurrounding each of said means for injecting vaporized fuel adjacentsaid dome and adapted to deflect air passing through said openings insaid dome toward said annular Walls.

1. An annular combustion chamber fed with liquid fuel and compressed aircomprising: two coaxial annular casings enclosing between them anannular space; two coaxial annular walls coaxial with said casings,housed within said annular space and the interval between which definesan annular combustion space through which the combustion gases areadapted to flow, said walls defining between them and the correspondingcasings annulAr passages; means adapted to supply said annular passageswith compressed air; a dome closing the combustion space at one endthereof; a plurality of means adapted to inject into the region of thecombustion space lying in the vicinity of the dome vaporized fuel, eachof said means having an outlet opening facing the dome and through whichlast-mentioned vaporized fuel is exhausted towards the dome in adirection substantially parallel to the axis of the annular walls, saidoutlet openings being distributed along an annular line extending atsubstantially equal distances from the said annular walls; and aplurality of nozzlelike ports extending across said annular walls andconnecting each of the annular passages with the annular combustionspace, a nozzlelike port across one annular wall registeringsubstantially radially with a corresponding nozzlelike port across theother annular wall and with a corresponding outlet opening through whichvaporized fuel is exhausted said dome having openings adjacent saidplurality of means for injecting vaporized fuel, deflector meanssurrounding each of said means for injecting vaporized fuel adjacentsaid dome and adapted to deflect air passing through said openings insaid dome toward said annular walls.